Discrete Wave Propagation In Quadratically Nonlinear Media

Discrete models are used in describing various microscopic phenomena in many branches of science, ranging from biology through chemistry to physics. Arrays of evanescently coupled, equally spaced, identical waveguides are prime examples of optical structures in which discrete dynamics can be easily observed and investigated. As a result of discretization, these structures exhibit unique diffraction properties with no analogy in continuous systems. Recently nonlinear discrete optics has attracted a growing interest, triggered by the observation of discrete solitons in AlGaAs waveguide arrays reported by Eisenberg et al. in 1998. So far, the following experiments involved systems with third order nonlinearities. In this work, an experimental investigation of discrete nonlinear wave propagation in a second order nonlinear medium is presented. This system deserves particular attention because the nonlinear process involves two or three components at different frequencies mutually locked by a quadratic nonlinearity, and new degrees of freedom enter the dynamical process. In the first part of dissertation, observation of the discrete Talbot effect is reported. In contrast to continuous systems, where Talbot self-imaging effect occurs irrespective of the pattern period, in discrete configurations this process is only possible for a specific set of periodicities. The major part of the dissertation is devoted to the investigation of soliton formation in lithium niobate waveguide arrays with a tunable cascaded quadratic nonlinearity. Soliton species with different topology (unstaggered all channels in-phase, and staggered neighboring channels with a pi relative phase difference) are identified in the same array. The stability of the discrete solitons and plane waves (modulational instability) are experimentally investigated. In the last part of the dissertation, a phase-insensitive, ultrafast, all-optical spatial switching and frequency conversion device based on quadratic waveguide array is demonstrated. Spatial routing and wavelength conversion of milliwatt signals is achieved without pulse distortions

Diffractionless Propagation In Low Loss Linbo3 Channel Waveguide Arrays

Diffractionless propagation in low loss LiNbO3 channel waveguide arrays was discussed. The maximum propagation angle achievable in an array was limited by the coupling coefficient. A beam of 60μm was launched into the array at different angles and the output beam was measured at the end of array

Parametric Light Mixing Experiments In Quadratic Nonlinear Waveguide Arrays

An efficient all-optical switching and routing scheme for low power optical signals based on parametric difference frequency generation in combination with the unique discrete dispersion characteristics of waveguide arrays was investigated experimentally

Discrete Quadratic Solitons In Waveguide Arrays

Quadratic soliton formation in an array of coupled PPLN channel waveguides was experimentally demonstrated for the first time. The discrete features of the solitons predicted by theory were observed. ©2000 Optical Society of America

Highly Localized Discrete Quadratic Solitons

We observe highly localized solitons in periodically poled lithium niobate waveguide arrays close to phase matching for second-harmonic generation. With fundamental and second-harmonic input in one channel the response indicates two distinguishable propagation schemes. Depending on the relative phase between the two input waves, a self-trapped beam emerges, resembling closely either the in- or the out-of-phase quadratic eigenmode of a single waveguide. A stable soliton propagates when the input waves are in phase. © 2005 Optical Society of America

Discrete Talbot Effect

The effects of discrete Talbot revivals in waveguide arrays was analyzed. Talbot self-imaging effect always occurs irrespective of the pattern period, in discrete configurations. In discrete structures, the periodicities leading to discrete Talbot revivals are those for which cosine of cos(2π/N) is a rational number. It was found that Talbot effect, fractional as well as fractal revivals are also known to occur at distances that are rational or irrational multiples of zT respectively

Observation Of The Discrete Talbot Effect

We report the first observation of the discrete Talbot effect in one-dimensional waveguide arrays. Recurrence for different input patterns was observed in very good agreement with simulations. No recursion occurs for the zero diffraction direction. © 2005 Optical Society of America

Observation Of The Discrete Talbot Effect

We report the first observation of the discrete Talbot effect in waveguide arrays. Recurrence for different input patterns was observed in good agreement with theory. The effect of nonlinearity on the Talbot dynamics was investigated. © 2005 Optical Society of America

Observation Of The Discrete Talbot Effect

We report the first observation of the discrete Talbot effect in waveguide arrays. Recurrence for different input patterns was observed in good agreement with theory. The effect of nonlinearity on the Talbot dynamics was investigated. © 2005 Optical Society of America